KR20050022109A - gunning castable refractory for dome part using fluid layer reduction furnace for reduction of iron ore - Google Patents

Abstract

PURPOSE: Provided are gunning castable refractories having chemical stability, resistance to corrosion and thermal shock, and mechanical strength in reductive atmosphere for forming the roofs of a fluid layer reduction furnace. CONSTITUTION: The gunning castable refractories for forming the roof(4) of a fluid layer reduction furnace(1) comprise 1.5-2.5wt.% of SiO2, less than 0.05wt.% of Fe2O3, 8-11wt.% of CaO and the remains of Al2O3, wherein SiO2 and Fe2O3 are used for application and resistance to CO gas, CaO is used for adhesion, and Al2O3 is used for high temperature strength. The resultant gunning castable refractories have characteristics of less than 2.55 of bulk specific gravity, more than 30% of porosity, more than 750kg/cm2 of compression strength, less than 10% of rebound loss, and CO resistance more than A-B, based on ASTM C288.

Description

Gunning castable refractory for dome part using fluid layer reduction furnace for reduction of iron ore}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gunning castable refractories for ceilings used in fluid layer reduction furnaces for reducing iron ore. Is a castable refractory used in the ceiling of a fluidized bed reduction furnace. It relates to a ganning castable refractory.

Modern steelmaking is called an indirect method, and once a molten iron is made, it is oxidized and decarburized to form steel. As an iron making method for making molten iron, a blast furnace method using coke as a fuel (blast furnace method) is used.

Figure 1 shows a conventional blast furnace method using a blast furnace, the pre-treatment process to make a solid pellets that can be loaded into the blast furnace as a lump of a certain size by crushing, ore, spectral briquettes, sintered iron ore. Coke is made from bituminous coal for use as fuel. The prepared pellets and coke are charged to the blast furnace to make a molten iron by fire.

The blast furnace method as described above is used as the best method in terms of mass production. However, the existing blast furnace method requires a large-scale facility for sintering and coke production together with the complexity of the process, resulting in economic burden such as high production cost, and also environmental pollution due to the process of sintering and coking. Problems such as emission of sulfur oxides (SO _X ), nitrogen oxides (NO _X ), and carbon dioxide (CO ₂ ), which are substances, occur.

A facility that can reduce the pre-treatment process of iron ore and exaggeration of coke, and directly reduce the spectral iron ore fluidization reaction in the natural state by changing the production method having the problems according to the blast furnace method has recently been named as a domestic brand at POSCO Pohang Works in Korea. The FINEX facility has recently been built and is in operation. Figure 2 shows the Finex process, Figure 3 shows an enlarged view of the fluidized bed reduction furnace in Figure 2, as shown in this, by reducing the iron ore through several stages of the fluidized bed reduction furnace (1) melting furnace (3) Charge it with powdered coal to make a molten iron. In the fluidized-bed reduction furnace, about 8mm or less of iron ore is transformed into reduced iron ore through the fluidized-bed reduction furnace divided into several stages, and this is a new steelmaking method to economically produce desired metals by molding and charging the pellets into a melting furnace. .

The fluidized bed reduction furnace (1) requires a refractory interior material according to a variety of use conditions, among which a high-pressure, high-temperature reducing gas is introduced and uniformly dispersed to flow the gas as a member for reducing the iron ore flow It consists of a dispersion plate 2 having a through hole and a ceiling part 4.

In the above facilities, the ceiling unit should be sprayed (hereinafter referred to as "ganning") construction because it is impossible to install the refractory material when forming and forming, and it is chemically stable under high-pressure, high-temperature reducing gas atmosphere and can withstand rapid temperature rise and low temperature conditions. Material required.

Therefore, this part is made of materials that have chemical durability, especially CO gas corrosion resistance, thermal shock resistance, and mechanical strength.

The conventional material applied to the ceiling has no material applied on a commercial scale as the facility itself is the world's first, but high alumina cascades have been used in the test facility, but the CO gas resistance and the thermal shock resistance are poor during use. There was a problem that due to shrinkage and cracking occurred during use.

Therefore, it is a reactor facility with annual production capacity of more than 100 min tons for large scale commercial production instead of small scale test. There should be no chemical reaction during use with various components contained in reducing gas and blue ore near the main temperature of 600 ~ 1000 ℃. It must have excellent wear resistance under high temperature and high velocity fluidization conditions of fine powder, and cracks may occur during intermittent operation rather than continuous operation, and thus, excellent thermal shock resistance that can withstand rapid temperature rise and low temperature due to resumption of operation is required.

In addition, due to the characteristics of the structure of the designed equipment, it is a structure that cannot be formed by forming a certain shape in advance, so this material should be secured as an indefinite material capable of ganning construction, and since it is a large construction body, it may be deformed during curing and drying after construction. It should not have the problem of exploding during drying.

Therefore, in non-test commercial facilities, harsher operating conditions, especially thermal shock conditions due to rapid temperature rises and low temperature operations, are expected. Therefore, the specific characteristics of the ceiling materials include a specific gravity of less than or equal to 2.55 and a dry compressive strength of 750 kg / Product design criteria with CO gas resistance of at least ² cm, porosity of at least 30% and ASTM C288 or higher shall be met.

The present invention is to provide a ceiling gunning castable refractory having a characteristic of chemically stable corrosion resistance and thermal shock resistance, mechanical strength in an atmosphere such as reducing gas by being different from the test ganning refractory.

The present invention for achieving the above object is 100% by weight, silica (SiO ₂ ) 1.5 to 2.5% by weight, iron oxide (Fe ₂ O ₃ ) 0.05% by weight or less, calcia (CaO) 8 to 11% by weight, The remainder is made of gunning castable refractories for the ceiling used in the iron ore reduction furnace, characterized in that the remainder is composed of alumina (Al ₂ O ₃ ).

In the above-mentioned composition, the composition range of silica (SiO ₂ ) and iron oxide (Fe ₂ O ₃ ) is limited to ensure construction characteristics and CO gas resistance characteristics. When the content of silica (SiO ₂ ) is 1.5% by weight or less When the ganning workability becomes poor and becomes 2.5 weight% or more, CO gas resistance under high temperature and high pressure falls, or sintering shrinkage occurs at high temperature due to the components of the free silica, thereby lowering the thermal shock resistance. And iron oxide (Fe ₂ O ₃ ) is for the CO gas resistance characteristics, 0.05% by weight or less is preferred.

Calcia (CaO) is CaO content contained in a material, For example, use of an alumina cement is mentioned. If the content of CaO is less than 8% by weight (i.e., using any kind of cement or raw material containing any CaO), the workability is not secured, and the rebound loss increases due to deterioration of the adhesion rate during the ganning construction. The required strength cannot be secured.

In addition, when the CaO content is more than 11% by weight, the construction properties and strength can be secured, but the amount of alumina (Al ₂ O ₃ ) is relatively reduced and the strength decreases at high temperatures, thereby reducing the thermal shock resistance.

Sintered alumina or fused alumina may be used to obtain alumina (Al ₂ O ₃ ) as the main component except for the above components. Since the ferrous ore reduction furnace applied to the present invention has a strong reducing condition, the alumina is 95% as a main raw material. The higher alumina mentioned above is more preferable.

In the present invention, the total composition is 100% by weight, and if the alumina component is too small as the main component excluding the subcomponent, the content of the other components is too high to obtain the above-mentioned characteristics, and the amount of CaO increases and the strength is increased. It is not preferable because it is lowered, and too much alumina component reduces the relative amount of other components, making it difficult to satisfy physical properties, and the specific gravity increases, and the porosity falls below 30%.

The present invention is made by the composition as described above, as a refractory ganning castable material for the ceiling for the reduction of fine iron ore, the specific gravity of the construction body less than 2.55, porosity 30% or more at 1000 ℃ temperature, dry compressive strength 750kg / cm ² More than. Alumina refractory quenching material having properties of ceiling rebound loss of 10% or less and CO resistance of ASTM C288 standard A to B or more is obtained.

The following is described according to the embodiment.

Table 1

  Comparative example   Example       Application example  Test facility  Commercial facility      Construction method  Inflow construction  Gunning construction Chemical composition (%) Al ₂ O ₃     93     87 SiO ₂      One     1.7 Fe ₂ O ₃    0.01    0.01 CaO     9.5 Specific gravity kg / m ²   2,900   2,520 Porosity (%) 1000 ℃     31 Compressive strength (kg / cm ² ) 110 ℃    450    800 1000 ℃    300    400 CO Gas Resistance ASTM C288     A      A Construction Rebound Loss (%)     10

※ Construction condition of pore body

Gunning Machine: Reed Gun

Air discharge pressure: 2kg / cm ² or more,

Water discharge pressure: 2 kg / cm ² or more

As described above, the present invention ensures the workability required in the basic design, the bulk specific gravity of the construction body is 2.55 or less, porosity 30% or more at 1000 ℃ temperature, dry compressive strength 750kg / cm ² or more. Alumina refractory quenching material having properties of ceiling rebound loss of 10% or less and CO resistance of ASTM C288 standard A to B or more is obtained.

1 is a schematic diagram of a manufacturing process according to a conventional blast furnace method

2 is a schematic diagram of a Finex process applied to the present invention

3 is an enlarged side view of the fluidized-bed reduction furnace in FIG.

1: fluidized-bed reduction furnace 2: dispersion plate 3: melting furnace 4: ceiling

Claims (1)

100 wt%, silica (SiO ₂ ) 1.5-2.5 wt%, iron oxide (Fe ₂ O ₃ ) 0.05 wt% or less, calcia (CaO) 8-11 wt%, the remainder is alumina (Al ₂ O ₃ ) Gunning castable refractories used for iron-iron ore reduction furnaces characterized by